Final Ratefactor meaning

[CommonMortal]

Hello, i wonder if someone can shed some light into this. I 've googled in vain. In x264 wiki it says that it describes the average QP.

Which isn't very illuminating. Some of the posts in doom9 that i found from many years ago, made me think that this could be an index of compressibility or indirectly quality.

Is this true? If yes, are there any "desirable" values for QP?

Thank you.

[Soichiro]

It is an estimation of quality. From what I know, it only shows up in the first pass of a bitrate-based encode, and it seems to be an estimation of the equivalent CRF that you would need to use to get the same size/quality that your bitrate-based encode produced. As with anything crf-based, a "good" value depends on what you're encoding, as well as how sensitive your eyes are to artifacts. Generally around 20 should be considered a fairly good value (lower values = better quality), but YMMV.

[CommonMortal]

Ah, THANK YOU! Your answer was perfectly clear, i couldn't ask for better one!

In deed, it appears at the end of the 1st pass.